1. Field of the Invention
The present invention relates to an Electromagnetic Interference (EMI) shielded enclosure and more particularly to an enclosure that provides significantly improved shielding of electromagnetic energy radiated from within the enclosure and substantially prevents the penetration therein of externally radiated electromagnetic energy.
2. Description of the Related Art
Enclosures are often used to house electrical and electronic systems including telecommunications equipment. Such enclosures are typically located either in a central office location or as a remote terminal exposed to the outside environment. The operation of the electronic systems housed in the enclosures often results in the radiation of electromagnetic energy. Many times the electromagnetic energy radiated by the enclosed circuitry can leak through an enclosure that does not provide sufficient shielding of such energy. Thus, these enclosures often become sources of undesired electromagnetic radiation that interfere adversely with other radiated signals (e.g., radio and television signals) and can also interfere with the proper operation of other electrical equipment within and without the enclosures; this is commonly referred to as Electromagnetic Interference (EMI).
It is well known that metallic enclosures provide some shielding from EMI. The electrically conductive surface of metallic enclosures serves to contain some of the radiated EMI within the enclosures. An ideal enclosure for containing electromagnetic radiation would have a continuously closed conductive envelope with no seams, apertures, openings, or gaps. Seams; aperture, openings, gaps and other discontinuities on the surface of these enclosures represent sources of EMI leakage and also tend to reduce the conductivity of the surfaces thus reducing the shielding capability of such enclosures. For example, the particular structural design of such enclosures often require the use of a door, cable-through holes, holes for connectors, ventilation openings and seams resulting from joined metallic surfaces.
Many EMI shielded enclosures are constructed with metallic surfaces or panels welded to each other and to metallic frames. The metallic frames are often constructed with interconnected structural members. The construction and manufacturing of EMI shielded enclosures constructed from structural frames and metallic panels welded to each other is often an expensive process. Moreover, EMI shielded enclosures made from structural frames and panels welded each other are inconsistent with a modular design approach in which the same or similar parts are used to construct enclosures of various sizes.
Further, there exists seam at the point where metallic panels are joined. It is well known that radiated electromagnetic energy can leak through the seams created by the joining of metallic surfaces. The metallic surfaces can be welded to each other, which depending on the length of the weld, may or may not seal the seams. Furthermore, as was stated previously, welding significantly adds to the cost of manufacturing EMI shielded enclosures.
Therefore, there is a need for a modularly designed EMI shielded enclosure that provides a substantially continuous conducting inner surface with properly sealed seams for an improved EMI shielding capability.